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<A HREF="contents.html"><IMG TITLE="Programming in Lua (first edition)" SRC="capa.jpg" ALT="" ALIGN="left"></A>This first edition was written for Lua 5.0. While still largely relevant for later versions, there are some differences.<BR>The third edition targets Lua 5.2 and is available at <A HREF="http://www.amazon.com/exec/obidos/ASIN/859037985X/theprogrammil3-20">Amazon</A> and other bookstores.<BR>By buying the book, you also help to <A HREF="../donations.html">support the Lua project</A>.
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<font color="gray">Programming in </font><font color="blue"> Lua</font>
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<td width="80%" align="center"><a href="contents.html#P1">Part I. The Language</a>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<a href="contents.html#4">Chapter 4. Statements</a></td>
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<p><h3>4.3.1 &ndash; <b>if</b> <b>then</b> <b>else</b></h3>

<p>An <b>if</b> statement tests its condition
and executes its <em>then-part</em> or its <em>else-part</em>
accordingly.
The else-part is optional.
<pre>
    if a&lt;0 then a = 0 end
    
    if a&lt;b then return a else return b end
    
    if line > MAXLINES then
      showpage()
      line = 0
    end
</pre>
When you write nested <b>if</b>s,
you can use <b>elseif</b>.
It is similar to an <b>else</b> followed by an <b>if</b>,
but it avoids the need for multiple <b>end</b>s:
<pre>
    if op == "+" then
      r = a + b
    elseif op == "-" then
      r = a - b
    elseif op == "*" then
      r = a*b
    elseif op == "/" then
      r = a/b
    else
      error("invalid operation")
    end
</pre>

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  Copyright &copy; 2003&ndash;2004 Roberto Ierusalimschy.  All rights reserved.
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